Titanium-aluminium-nitride(Ti_(1-x)Al_(x)N)coatings were deposited by close-field un balanced magnetron sputtering on M42 steel substrates and WC-6wt%Co inserts at 450℃.The tribological behavior was analyzed by slidi...Titanium-aluminium-nitride(Ti_(1-x)Al_(x)N)coatings were deposited by close-field un balanced magnetron sputtering on M42 steel substrates and WC-6wt%Co inserts at 450℃.The tribological behavior was analyzed by sliding against steel and WC-6wt%Co balls,while the turning performance was evaluated by a conventional tu rning machine at high cutting speeds without using coolants.In the tribological tests,the formation of transfer layer and the variations of hardness of the co atings played an important role for sliding against steel balls.For the coating s sliding against WC-6wt%Co balls,the Ti-Al-N coatings showed a similar frictio n coefficient,but the TiN coating exhibited a lower value.The difference could be explained by the tri-oxidation wear mechanism.In the turning tests,a super ior cutting performance of the coating was found at x=0.45,which endured 38 min utes before the tool flank wear reached the maximum value of 0.3mm,whereas only 20 minutes were endured for the TiN coating.The excellent performance of the c oatings in the turning tests could be explained by the enhanced mechanical prope rties and oxidation/diffusion resistance of the coatings.展开更多
Several nc-TiN/a-TiB2 thin films comprised of nanocrystalline (nc-) TiN and amor phous (a-) TiB2 phases were deposited on Si(100) at room temperature by reactive unbalanced dc magnetron sputtering, followed by vacuum ...Several nc-TiN/a-TiB2 thin films comprised of nanocrystalline (nc-) TiN and amor phous (a-) TiB2 phases were deposited on Si(100) at room temperature by reactive unbalanced dc magnetron sputtering, followed by vacuum annealed at 400, 600, 80 0 and 1000℃ for 1h, respectively. Effects of B content on microstructure, mecha nical behaviors and thermal microstructure stability have been investigated by X -ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and nanoindentation measurements. The results indicated that B addition greatly affected both microstructure and mechanical behavior of nc-Ti N/a-TiB2 thin films. With increasing B content the grain size decreased. A maxim um hardness value of about 33GPa was obtained at B content of about 19at.%. The improved mechanical properties of nc-TiN/a-TiB2 films with the addition of B int o TiN were attributed to their densified microstructure with development of fine grain size. Only addition of sufficient B could restrain grain growth during an nealing. High B content resulted in high microstructure stability. The crystalli zation of amorphous matrix occurred at about 800℃, forming TiB or TiB2 crystall ite, depending on B content. Before that no change in bonding configuration was found.展开更多
Friction and sliding wear behaviour of Ti-B-N coatings against AISI440C steel ba ll and WC-6wt%Co ball were studied by using pin-on-disk tribometer along with mi crostructure characterization using optical microscopy ...Friction and sliding wear behaviour of Ti-B-N coatings against AISI440C steel ba ll and WC-6wt%Co ball were studied by using pin-on-disk tribometer along with mi crostructure characterization using optical microscopy (OM), scanning electron m icroscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It is shown that the wear resistance of film depended on the wear mechanism. In the case of AISI440C steel, adhesive wear were pre-dominant and the wear rate increased sharply to a maximum when N content reach ~38at.%. This might be related to the change of fi lm microstructure and phase configuration, so the least adhesive transfer of tri bo-film was observed. If WC-6wt%Co ball was used, less deformation wear debris w as observed, this was responsible for the rise of wear rate. Despite of differen t wear modes, friction coefficients in both cases were found to depend mainly on the formation and the amount of h-BN phase. Elemental analysis by energy disper sive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) revealed that oxygen participated in the wear behavior by reacting with films to form the deb ris comprised of various types of Ti oxide including TiO, TiO2 and Ti2O3 , which increased wear resistance.展开更多
Multilayer thin films of TiN/SiNx have been deposited onto heated Si 100 substra tes (200℃) by reactive dc-magnetron sputtering from Ti and Si targets in an Ar- N2 gas mixture. The rotation speed of the substrate hol...Multilayer thin films of TiN/SiNx have been deposited onto heated Si 100 substra tes (200℃) by reactive dc-magnetron sputtering from Ti and Si targets in an Ar- N2 gas mixture. The rotation speed of the substrate holder was varied from 1 to 20rpm, while target currents were held constant, to produce bilayer periods vary ing from approximately 22 to 0.6nm. These multilayer films were characterized by atomic force microscopy (AFM), cross-sectional transmission electron microscopy (TEM), scanning electron microscopy (SEM), and microhardness measurements. TEM and SEM studies showed elimination of columnar structure in TiN, owing to the in corporation of amorphous SiNx layers. The crystallinity of TiN and amorphous nat ure of SiNx were confirmed by high resolution TEM. An optimum rotation speed was observed, at which hardness was a maximum. The resulting bilayer period was fou nd to be approximately 1.6nm, which resulted in a significant improvement in mic rohardness (~57GPa). The rms surface roughness for this film was less than 1.5nm .展开更多
Correlation bet ween the elastic and the vibronic behavior of TiO_(2) and their responses to thevariation of crystal size,applied pressure,and measuring temperature has been investig ated basedon the bond order-length...Correlation bet ween the elastic and the vibronic behavior of TiO_(2) and their responses to thevariation of crystal size,applied pressure,and measuring temperature has been investig ated basedon the bond order-length-strength correlation mechanism.Theoretical reproduction of themeasurements clarified that.(i)the elastic modulus(B)and the Raman shifts(△ω)are stronglycorrelated and we can know either one of the B or the △ω from the other;(i)the under-coordination induced cohesive energy loss and the energy density gain in the surface up to skindepth determines the size effect;(ii)bond expansion and bond weakening due to thermalvibration originat es the thermally softened elastic modulus and the Raman shifts;and(iv)bondcompression and bond strengthening results in the mechanically stiffened elastic modulus and theRaman shifts.With the developed premise,one can predict the changing trends of the concernedproperties with derivatives of quantitative information of the atomic cohesive energy,bindingenergy density,Debye tempera ture,and nonlinear compressibility of the specimen.展开更多
基金The authors wish 10 thank the use of the facilities in ACARL which is suppored by the Innovation Technology Fund of Hong KongPWS acknowledges the support of the research scholarship from the City University of Hong Kong and ME thanks the financial support by a grant awarded by the Research Grant Council of the Hong Kong Special Administrative Region,China(No.CityU 1180/01E)
文摘Titanium-aluminium-nitride(Ti_(1-x)Al_(x)N)coatings were deposited by close-field un balanced magnetron sputtering on M42 steel substrates and WC-6wt%Co inserts at 450℃.The tribological behavior was analyzed by sliding against steel and WC-6wt%Co balls,while the turning performance was evaluated by a conventional tu rning machine at high cutting speeds without using coolants.In the tribological tests,the formation of transfer layer and the variations of hardness of the co atings played an important role for sliding against steel balls.For the coating s sliding against WC-6wt%Co balls,the Ti-Al-N coatings showed a similar frictio n coefficient,but the TiN coating exhibited a lower value.The difference could be explained by the tri-oxidation wear mechanism.In the turning tests,a super ior cutting performance of the coating was found at x=0.45,which endured 38 min utes before the tool flank wear reached the maximum value of 0.3mm,whereas only 20 minutes were endured for the TiN coating.The excellent performance of the c oatings in the turning tests could be explained by the enhanced mechanical prope rties and oxidation/diffusion resistance of the coatings.
文摘Several nc-TiN/a-TiB2 thin films comprised of nanocrystalline (nc-) TiN and amor phous (a-) TiB2 phases were deposited on Si(100) at room temperature by reactive unbalanced dc magnetron sputtering, followed by vacuum annealed at 400, 600, 80 0 and 1000℃ for 1h, respectively. Effects of B content on microstructure, mecha nical behaviors and thermal microstructure stability have been investigated by X -ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and nanoindentation measurements. The results indicated that B addition greatly affected both microstructure and mechanical behavior of nc-Ti N/a-TiB2 thin films. With increasing B content the grain size decreased. A maxim um hardness value of about 33GPa was obtained at B content of about 19at.%. The improved mechanical properties of nc-TiN/a-TiB2 films with the addition of B int o TiN were attributed to their densified microstructure with development of fine grain size. Only addition of sufficient B could restrain grain growth during an nealing. High B content resulted in high microstructure stability. The crystalli zation of amorphous matrix occurred at about 800℃, forming TiB or TiB2 crystall ite, depending on B content. Before that no change in bonding configuration was found.
文摘Friction and sliding wear behaviour of Ti-B-N coatings against AISI440C steel ba ll and WC-6wt%Co ball were studied by using pin-on-disk tribometer along with mi crostructure characterization using optical microscopy (OM), scanning electron m icroscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It is shown that the wear resistance of film depended on the wear mechanism. In the case of AISI440C steel, adhesive wear were pre-dominant and the wear rate increased sharply to a maximum when N content reach ~38at.%. This might be related to the change of fi lm microstructure and phase configuration, so the least adhesive transfer of tri bo-film was observed. If WC-6wt%Co ball was used, less deformation wear debris w as observed, this was responsible for the rise of wear rate. Despite of differen t wear modes, friction coefficients in both cases were found to depend mainly on the formation and the amount of h-BN phase. Elemental analysis by energy disper sive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) revealed that oxygen participated in the wear behavior by reacting with films to form the deb ris comprised of various types of Ti oxide including TiO, TiO2 and Ti2O3 , which increased wear resistance.
文摘Multilayer thin films of TiN/SiNx have been deposited onto heated Si 100 substra tes (200℃) by reactive dc-magnetron sputtering from Ti and Si targets in an Ar- N2 gas mixture. The rotation speed of the substrate holder was varied from 1 to 20rpm, while target currents were held constant, to produce bilayer periods vary ing from approximately 22 to 0.6nm. These multilayer films were characterized by atomic force microscopy (AFM), cross-sectional transmission electron microscopy (TEM), scanning electron microscopy (SEM), and microhardness measurements. TEM and SEM studies showed elimination of columnar structure in TiN, owing to the in corporation of amorphous SiNx layers. The crystallinity of TiN and amorphous nat ure of SiNx were confirmed by high resolution TEM. An optimum rotation speed was observed, at which hardness was a maximum. The resulting bilayer period was fou nd to be approximately 1.6nm, which resulted in a significant improvement in mic rohardness (~57GPa). The rms surface roughness for this film was less than 1.5nm .
基金support from the Special Project for Nanotechnology of Shanghai(No.1052nm02700)the Key laboratory of new ceramics and fine processes at Tsinghua University and MOE(RG15/09)of Singapore is gratefully acknowledged.
文摘Correlation bet ween the elastic and the vibronic behavior of TiO_(2) and their responses to thevariation of crystal size,applied pressure,and measuring temperature has been investig ated basedon the bond order-length-strength correlation mechanism.Theoretical reproduction of themeasurements clarified that.(i)the elastic modulus(B)and the Raman shifts(△ω)are stronglycorrelated and we can know either one of the B or the △ω from the other;(i)the under-coordination induced cohesive energy loss and the energy density gain in the surface up to skindepth determines the size effect;(ii)bond expansion and bond weakening due to thermalvibration originat es the thermally softened elastic modulus and the Raman shifts;and(iv)bondcompression and bond strengthening results in the mechanically stiffened elastic modulus and theRaman shifts.With the developed premise,one can predict the changing trends of the concernedproperties with derivatives of quantitative information of the atomic cohesive energy,bindingenergy density,Debye tempera ture,and nonlinear compressibility of the specimen.
